Tamper-proof closures



April 1966 v E. w. MERRILL 3,244,307

TAMPER-PROOF GLOSURES Filed Dec. 27, 1963 United States Patent 3,244,307 TAMPER-PROUF CLOSURES Edward W. Merrill, Belmont, Mass, assignor to W. R. Grace & 0)., Cambridge, Mass, a corporation of Connecticut Filed Dec. 27, 1963, Ser. No. 333340 8 Claims. (Cl. 215-46) This invention relates to container closures and particularly to closures for glass jars which cannot be removed from the jar without leaving positive evidence that the container has been opened.

Many food products are packed in glass jars and sealed with closures either of the pry-off or the twist-oif type. Since the pry-off closure is usually so deformed by the purchaser in the art of prying it off that it cannot be used to reseal the jar, there has been an insistent demand on the part of the consumer that the jar be reclosable to permit storage of whatever remains of its original contents.

The twist-off type of closure can be made to require but a minimum efforts in twisting off the cap. However convenient this may be to the consumer, this type of pack faces a continuing and increasing hazard: too many jars are opened and reclosed while on the shelves of the selfservice store. This practice has become of such deep concern to responsible food packers, food merchants, and public health groups that the removal force required to twist off such a closure has purposefully been made quite high. This, in turn, has brought consumer complaint because a tool or a jar wrench is usually required to remove the closure.

The closure of the present invention cannot be opened .unless a tear-out section of the closure is removed. This gives such a clear indication thatthe jar has been tampered with that few persons would pick up such a jar, much less purchase it. On theother hand, relatively little force is required to remove the tear-out panel, so that it is more convenient for the consumer to open than the closures now in use.

In addition to the requirement that the sealing element .be destroyed before the jar can be opened, one embodiment of the invention includes the provision of a temporary, non-hermetic closure which satisfies the requirements of a reclosable jar for the storage of part of the jar contents. It is a further object of the invention to increase the resistance of the path through which oxygen must diffuse before it can reach the interior head space of the container, to a degree better by an order of magnitude than obtainable in any currently available twist-off or pry-01f closure for jars. Another object of the invention is the provision of a closure for glass containers which employs sealing compositions of lesser thickness and volume than heretofore possible.

These and other objects will become apparent from the specification and from the drawings in which FIG; 1 is an elevation of the sealed container.

FIG. 2 is a top plan view of the closure.

FIG. 3 is a vertical section of the closure on the ilne 33 on FIG.-2.

FIG. 4 is an enlarged partial vertical cross-section through the mouth portion of the preferred form of the invention.

FIG. 5 is an enlarged partial vertical crosss-ection of the mouth portion of an alternative form, and

. FIG. 6 is a vertical cross-section of one form of closing disc.

(In FIGS. 4 and 5, the space shown between the various parts is for clarity in illustration only.)

The term sealing surface as used in the container industry refers to that portion of the finish adjacent the mouth of a jar which forms the actual contacting surface of the jar with the sealing element of the closure. The Word finish means the entire mouth portion of a container. It refers to the area which extends from the shoulder of the jar to inside the mouth or neck.

The container of the present invention is formed of glass. Instead of the conventional finish of the screwcap container, the improved container 10 has a sealing surface 11 comprising a single bead of a suitable configuration to permit the metal of the closure to be wiped over and locked about it. The bead can be, and preferably is, ovoid in shape and projects outwardly beyond the wall 12. In one embodiment, the sealing surface terminates in a step 13 the function of which is to form a seat for a temporary closure used in storage. In another especially preferred embodiment where a temporary closure for storage is provided, the sealing surface terminates in step 13 below which is a second step 14 upon which the temporary closure is seated.

The closure element 15 is a disc of ductile metal, usually aluminum. The periphery of the disc is surrounded by a channel 16, the outer wall 17 of which is formed as an inturned curl 26. Channel 16 is lined on conventional lining machinery with a flexible and distortable sealing com-position 18. The mouth-closing panel portion 19 is provided with a suitable tear-out section. This may be a sector or have any convenient shape, but in the preferred embodiment the tear-out section is substantially is employed for storage purposes, a disc 23 which seats either on step 13 or upon shoulder 14, preferably the latter, is placed under the metal. This temporary closure may be a fiat disc provided with suitable means for removing and replacing it, such as a pull-tab or the like. Conveniently, the disc 23 may have a distorted crosssection as shown in FIG. 6 with a centrally projecting portion 24 which forms a small handle. The disc fit in their respective seats (13 or 14) with a press or friction fit. Disc can be made of any rigid material impervious to foodstuffs packed in the jar but the cheapness, moldability, and imperviousness of rigid polyethylene closedcell foam makes it especially suitable.

Ordinarily, the metal of the closure will have sufiicient and rigidity to resist implosive force. For example, it will generally have thickness between about 4 to 20 mils and be of suitable temper for ductility. In such cases, the function of the disc 23 becomes solely that of a temporary cover when part of the contents are to be stored, but the disc does offer support for the closure, and when very ductile or thin metal is used, support may be desirable.

The composition used to form the seal 18 in the present closure is a low modulus sealing composition. A low modulus composition is conveniently defined for the present purposes as one having a tension after its placement and drying, or in its solid form, of not more than 300, preferably less than 100, pounds per square inch of original cross-section measured at room temperature at percent elongation under a rate of elongation of 3.3 percent per second. In general, known sealing compositions having the requisite aforementioned low modulus can be employed. Among such are compositions based upon natural rubber, synthetic rubber such as styrene-butadiene rubbers, butadiene-acrylonitrile rubbers, plastisols of vinyl halide polymers such as polyvinylchloride, and similar sealing compositions. For the most efiective results, however, it is preferred to employ sealing compositions which not only are capable of adhering to the metal of the closure, but also are capable of adhering to the glass. Such compositions are more effective in preventing the diffusion of oxygen, are more effective in preventing the removal of the metal from the sealing surface when the tear-out section or panel is disengaged so that the portion of the closure which is not a part of the tear-out section is permanently adhered to the sealing surface of the container, and possess other advantages such as good flow and conformability when the closure is wiped or locked about the sealing surface. Sealant compositions which are not crosslinked and do not become so are also especially preferred because of their greater adhesion both to the metal and to the glass. In this connection, sealant compositions having the defined modulus, adhesion, and non-crosslinked characteristics which are based on styrene-butadiene synthetic rubbers are especially suitable. It is to be understood that the sealing compositions may contain the usual additives such as fillers, pigments, diluents, stabilizers, antioxidants, viscosity modifiers, and the like so long as the above criteria are met.

In one method of utilizing the invention, a container is packed and sealed as follows: food is placed in a jar, leaving the usual head space. When the supporting disc 23 is employed, it is then inserted. The closure, now with its peripheral channel 16 lined with the sealing composition, is then placed over the mouth of the jar. If the filled container is sealed in the conventional exhaust box, air is withdrawn from the head space by the vacuum in the exhaust box, and passes out of the container between the closure and the glass. When the temporary sealing disc 23 is employed, air passes between the disc 23 and the step 13 or 14 because the contact between the disc and the glass is not hermetic, and the air path between the lined closure 15 and the glass has not yet been closed.

When the proper degree of vacuum has been reached, the fingers or wipers associated with the vacuum closing machine press downwardly and inwardly on the skirt 2-5 and push it into permanent contact with the sealing surface. Their action also wraps the curl 26 about the sealing surface 11. Thus, the closure 15 is not only adhesively but also mechanically locked onto the container 10. A closing device using a top pressure pad followed by the action of a descending conical wedge together with a closing roll also will force the sealing composition 18 into sealing contact with the sealing surface and lock the curl 26 about the bead sealing surface 11.

In that embodiment wherein both the step 13 and shoulder 14 are employed in conjunction with the temporary sealing disc 23 and a circular peripheral score, or scores 20, in the panel portion 19, the disc may be adhesively secured to the metal closure prior to its application to the container by a narrow band 27 of adhesive applied to the top of the disc 23 adjacent its margin. If this band is substantially co-extensive with the peripheral circular scores 20, tearing out the scored or panel portion 19 of the metal closure destroys the adhesive contact between the panel portion 19 and the disc 23. Since the disc 23 is now unobstructed, it may be lifted 01f from its seat on the shoulder 14. When the customer is about to use the jar, the pull-tab 22 is lifted and given a sharp jerk. This breaks the panel loose at the score lines and exposes the entire area of the disc 23. The disc is then lifted off shoulder 14 and as much of the contents of the jar as may be necessary is removed. The tear-out portion 19 is discarded, but the disc 23 may be reinserted on its seat and used as an effective cover when the jar is placed in storage.

The amount and distribution of the lining is important. It should be noticed that the seal is not only thinner, but has a much greater transverse extent than that of the seals commonly used on press-on or screw-on closures, and that the sealing material extends over the entire extent of the sealing surface of the container. As a consequence, the diffusion path of any gas, particularly oxygen, which is deleterious is made much longer than in the conventional combination of jar and closure. The sealant material is so distributed in the sealing portion of the closure that the ratio of the average width, measured radially to the average thickness, measured normal to the closure surface, is at least 5 to 1 When the closure is in its final sealed relationship to the closure finish.

The low modulus properties of the sealing compound in combination with the use of a ductile metal closure having its curl wiped about the container finish, leads to the important result that the thickness of the sealing gasket between the container and the metal closure lies between and of the thickness of gaskets presently used in twist-off or pry-off caps.

Ordinarily, the solid volume of sealant material applied to the closure will lie between 30 and 200 cubic millimeters, evenly distributed in the channel of a closure of the so-called 202 size (about 2% inches in diameter), and will be proportionately more or less in closures of greater or lesser diameters. Even with these small amounts of sealant material, excellent sealing characteristics are obtained. The closure and the manner of its closing leads to the important result that oxygen permeability is reduced by a factor of 25 to 50-fold over that of conventional pry-off or twist-off closures.

The shelf life of foods packed in this manner is lengthened. More months must elapse before significant amounts of oxygen can reach the jar contents. The low modulus sealing compositions, especially the preferred compositions which adhere to and wet both the jar and the closure, form a seal impervious to biological contamination. The material flows into, fills and plugs the microscopic irregularities which sometimes, in the absence of adhesive contact, become the microscopic diffusion channels through which oxygen and microbiological contaminants gain entrance.

Typical, but nondimiting, container sealing compositions employable and other illustrations of this invention are as follows:

EXAMPLE I Parts by weight Butadiene styrene rubber (hexane soluble 23% styrene content) 100 Carbon black master batch (20% carbon black,

% above rubber) 0.5

Nonylated triphenyl phosphite (antioxidant) 1 Titanium dioxide 8.4 Hydrated aluminum silicate 50 Poly-(betapinene)-(M.P. 115 C.) 5O Stearic acid 4 Zinc oxide l0 High-purity hexane N-hexane) 408.4 Anhydrous denatured alcohol 10.5

EXAMPLE II Parts by weight Butadiene styrene rubber (hexane soluble 23% styrene content) 75 Butadicne styrene rubber (hexane insoluble 45% styrene content) 25 Carbon black master batch (20% carbon black,

80% above rubber) 0.5 Nonylated triphenyl phosphite (antioxidant) 1.0 Poly-(betapinene)(M.P. C.) 50

Parts by weight Zinc oxide 92 High-purity hexane (85% N-hexane) 353 Anhydrous denatured alcohol 12.2

The viscosity of the above composition, Brookfield #3 spindle at 60 rpm. and 80 F., was 2000 centipoises. The modulus of this composition is less than 100 pounds per square inch when measured as set out in the foregoing example.

EXAMPLE III Parts by weight Polyvinylchloride resin (plastisol grade) (Exon 654) 100 Dibutyl sebacate 100 These materials are milled together in an edge-running mill until a smooth, uniform dispersion of fine particle resin in the plasticizer results. The fluid paste is lined in the channel of the end. Subsequent to lining, the closms is heated briefly to flux' the plastisol and is then cooled. The modulus of this composition was 300 pounds per square inch of original cross-section at room temperature, at 100 percent elongation at a rate of elongation of 3.3 percent per second.

EXAMPLE IV Parts by weight The viscosity of the composition measured on a Brookfield viscometer with a #3 spindle at 60 rpm. and at 80 F. was 2000 centipoises. The modulus of this sealing composition is less than 100 pounds per square inch when measured as set out in Example I.

Tests on the closures were performed in the following manner: the test jars were preheated in an oven maintained at 220 F. for 1-5 to 20 minutes. The closures were then crimped on to the test jars with a top pressure of 100 p.s.i., while the curl was wiped under the finish (bead) of the test jar. Vacuum was drawn to 25 inches. Loss in vacuum was measured by the conventional vacuum puncture test at the end of one hour, 12 hours, and three weeks. An average of tests made on jars sealed with closures having linings of Example I, weighing from 47 to 188 rngs., showed no loss of vacuum after one hour, 12 hours, or three weeks. Blow-off pressures were tested by injecting air into the head space. When air was admitted rapidly, the closure buckled at p.s.i. internal pressure, and blew off at pounds. When air was admitted gradually, the closure started to leak at 10 p.s.1. internal pressure, buckled at 16 p.s.i., and blew off at 22 psi. The tests thus demonstrated that the closure afforded ample protection for the foodstuiis. In further tests comparing the performance of sealing Compositions, it. was found that the plastisols exhibited a wider spread of retained vacuum values than did those compositions which adhered both to the metal and the glass.

I claim:

1. A sealed container having an open mouth surrounded by an outwardly extending sealing surface, a metallic closure having a mouth closing panel and a surrounding downturned peripheral curl, an adhesive sealing substance interposed between said sealing surface and the closure 6 and adherent to both closure and container, the curl of said closure being enfolded and locked about the sealing surface thereby sealing the container and preventing opening unless the panel is removed head space above the container contents at a subatmospheric pressure, a step in the interior finish of said container, a supporting disc seated on said step, the said disc affording support against implosion of the closure and capable, after the container is opened, of being reinserted on its seat to form a temporary cover for the container.

2. A container closure formed of a ductile metal having a mouth-closingpanel portion, a channel surrounding the panel terminating in an inwardly directed peripheral curl, a score formed in the surface of the panel substantially coextensive with the boundary of the panel, a pull-tab connected to the panel, a sealing composition forming a continuous ring in said channel and adhered to the closure, the solid volume of said sealing composition being not more than 200 cubic mm. nor less than 30 cubic mm. for containers with mouth finish diameters of 2% inches and proportionately more or less in closures of greater or lesser diameter, and having a ratio of average width measured radially to average thickness measured normal to the closure of at least 5-1 when the closure is in sealing relationship with a container and a supporting disc substantially co-extensive with said panel secured to the interior surface of said panel only by a zone of adhesive at its periphery, whereby removal of the panel portion of the closure from a sealed container will expose the entire area of the supporting disc.

3. A closure for glass containers capable of producing seals having high oxygen impermeability, formed of ductile metal having a mouth-closing panel portion, and a peripheral portion including a channel surrounding the panel and terminating in an inwardly directed curl, a low modulus lining composition adhered to and substantially coextensive with the interior wall of said channel, the surface area of the peripheral portion being sufficient, when wiped into sealing relationship, substantially to cover the entire sealing surface of .a co-operating container, the said sealing composition being capable of adhering to glass when wiped into contact therewith, and having a solid volume of nor more than 200 cubic mm. nor less than 30 cubic mm. for containers with mouth finish diameters of 2% inches and proportionately more or less in closures of greater or lesser diameter, the modulus of the said sealing composition being not greater than 300 lbs. p.s.i. of original cross section measured at room temperature at percent elongation under a constant rate of elongation of 3.3 percent per second.

4. A closure as claimed in claim 3 having a tear-out portion defined by a score surrounding the margin of the panel and means to disengage the tear-out portion whereby the entire mouth-closins panel area of the closure may be removed but leave the peripheral portion of said closure mechanically and adhesively secured to the container.

5. A sealed container comprising a glass container element having body and mouth portions, the said month portion terminating in a sealing surface consisting of a single, outwardly directed head, a closure formed of duetile metal having panel and peripheral portions, the said panel portion normally occupying the mouth area and having a tear-out section to permit opening the container, a container sealing composition interposed between said peripheral portion and said bead adhered both to the glass and to the closure, the peripheral portion being enfolded about said bead, the said sealing composition and the metal in the said peripheral portion covering substantially the entire sealing surface presented by said bead, the width of the sealing composition measured radially being at least five times its thickness measured normal to the closure, whereby a diifusion resistant path is established and oxygen diifusion into a vacuumized head space is reduced by a major factor when compared to conventional top seal closures.

6. A sealed container including a glass container element'having mouth and body portions and having a single peripheral bead extending outwardly from the mouth, and forming a sealing surface, a metallic closure having mouthclosing panel and peripheral sealing portions overlying respectively said mouth and said bead, a low modulus glass and metal adherent sealing composition interposed between the closure and the head in adhesive contact with and substantially covering the entire extent both of the bead and the interior surface of the said peripheral portion, the said peripheral portion being bent beneath and conformed to the configuration of the head, the ratio of the width of said sealing composition measured radially to the thickness of the composition measured normal to the closure surface being at least -1, the solid volume of said sealing composition being restricted to limits lying between 30 and 200 cubic mm. for containers of 2 /8 inch mouth diameter and having the same proportionate limits for containers of other mouth dimensions, whereby the sealed container is highly resistant to oxygen diffusion.

7. A sealed container as claimed in claim 5, wherein the interior mouth portion of the container is provided with a shoulder, an impervious disc seated on the shoulder, a score surrounding the margin of the panel, grasping means attached to the panel to permit detachment of the panel whereby the entire area of the disc may be exposed and means to permit the lifting of the disc from said shoulder.

8. A container having an open mouth, a sealing surface extending outwardly from the mouth, upper and lower steps formed in the interior finish of said mouth, a supporting disc seated on the lower step, a metallic closure extending across the mouth, the said closure comprising a mouth closing panel, a surrounding channel and a peripheral curl, a sealing composition interposed between the sealing surface and the interior wall of said channel the said sealing composition being capable of adhering to glass when wiped into contact therewith and having a solid volume of no more than 200 cubic mm. or less than 30 cubic mm. for containers with mouth finish diameters of 2 /8 inches and proportionately more or less in closures of greater or lesser diameter; a score formed in the surface of said closure at the margin of the panel portion; a pulltab aflixed to the panel, the channel and curl portions of said closure being enfold-ed and locked about the sealing surface thereby sealing the container and preventing opening unless the panel is removed, the said supporting disc thereafter functioning as a storage cover.

References Cited by the Examiner UNITED STATES PATENTS 1,136,418 4/1915 Gomber 215- 2,256,483 9/ 1941 Johnston. 2,387,730 10/ 1945 Alderson. 2,428,782 10/ 1947 Browne 21540 2,456,972 12/ 1948 Maeder, et al. 2l5'40 2,751,102 6/1956 Kihm 21546 2,946,478 7/1960 Clair et a l.

FOREIGN PATENTS 222,664 7/ 1959 Australia.

236,093 10/1959 Australia.

512,315 10/1920 France.

308,078 3/1929 Great Britain.

557,162 11/ 1943 Great Britain.

840,132 7/1960 Great Britain.

468,395 1/ 1952 Italy.

THERON E. CONDON, Primary Examiner.

J. M. CASKIE, Assistant Examiner. 

1. A SEALED CONTAINER HAVING AN OPEN MOUTH SURROUNDED BY AN OUTWARDLY EXTENDING SEALING SURFACE, A METALLIC CLOSURE HAVING A MOUTH CLOSING PANEL AND A SURROUNDING DOWNTURNED PERIPHERAL CURL, AN ADHESIVE SEALING SUBSTANCE INTERPOSED BETWEEN SAID SEALING SURFACE AND THE CLOSURE AND ADHERENT TO BOTH CLOSURE AND CONTAINER, THE CURL OF SAID CLOSURE BEING ENFOLDED AND LOCKED ABOUT THE SEALING SURFACE THEREBY SEALING THE CONTAINER AND PREVENTING OPENING UNLESS THE PANEL IS REMOVED HEAD SPACE ABOVE THE CONTAINER CONTENTS AT A SUBATMOSPHERIC PRESSURE, A STEP IN THE INTERIOR FINISH OF SAID CONTAINER, A SUPPORTING DISC SEATED ON SAID STEP, THE SAID DISC AFFORDING SUPPORT AGAINST IMPLOSION OF THE CLOSURE AND CAPABLE, AFTER THE CONTAINER IS OPENED, OF BEING REINSERTED ON ITS SEAT TO FORM A TEMPORARY COVER FOR THE CONTAINER. 